As a surface light emitter with a substantially two dimensional radiation surface using an electroluminescence (hereinbelow, described as EL), an organic EL device or an inorganic EL device is known. As the surface light emitter constituted by the organic EL device, a surface light emitter is known including a transparent substrate, a transparent electrode provided on a surface of the transparent substrate, a rear surface electrode that is provided to be spaced from the transparent electrode and is formed of a metal thin film, and a light emitting layer that is provided between the transparent electrode and the rear surface electrode and contains a light emitting material of an organic compound.
In the surface light emitter, when a hole supplied from the transparent electrode and an electron supplied from the rear surface electrode are coupled at the light emitting layer, the light emitting layer emits light. Light emitted from the light emitting layer transmits through the transparent electrode and transparent substrate, and is extracted from a radiation plane (a surface of the transparent substrate). In addition, it is also reflected by the metal thin film of the rear surface electrode, and then transmits through the light emitting layer, the transparent electrode, and the transparent substrate, and is extracted from the radiation plane.
However, in this surface light emitter, when an angle of incidence of light that is incident to the transparent electrode, the transparent substrate, external air, and the like is larger than a critical angle that is determined by a refractive index of a material that is an incidence source and a refractive index of a material that is an incidence destination, the light is totally reflected on an interface between the light emitting layer and the transparent electrode, an interface between the transparent electrode and the transparent substrate, an interface (radiation plane) between the transparent substrate and the external air, and the like, and is trapped inside the surface light emitter. Therefore, there is a problem in that a part of light is not extracted to the outside, and thus light extraction efficiency is low.
As a surface light emitter to solve this problem, the following surface light emitter has been suggested.
An organic EL device in which a diffraction grating constituted by a periodic uneven structure is formed on a surface of a transparent electrode side of a transparent substrate (Patent Literature 1).
In that organic EL device, the light emitted from the light emitting layer is diffracted by the diffraction grating in such a manner that the angle of incidence of the light that is incident to the transparent electrode, the transparent substrate, and the external air decreases, and thus the total reflection on the respective interfaces is reduced, and the light extraction efficiency is improved.
In addition, as a method for obtaining a large size optical article having an uneven surface structure and producing it with favorable productivity, the following method has been suggested.
A method for producing an anti-glare film by transferring, onto a surface of a transparent resin film, an uneven structure of a mold having an uneven structure which is formed by colliding microparticles on a surface plated with copper or nickel (Patent Literatures 2 and 3).